First of all, observe that all fractions exist as long as b is not zero.
Multiply both numerator and denominator of the first fraction by 3:
Now all fractions have the same denominator. Under the assumption that b is not zero, multiply both sides by 3b:
Subtract 3b from both sides:
Subtract 2 from both sides:
Divide both sides by 2:
Answer: Downhill:10mph Uphill:5mph
Step-by-step explanation:
We are looking for Dennis’s downhill speed.
Let
r=
Dennis’s downhill speed.
His uphill speed is
5
miles per hour slower.
Let
r−5=
Dennis’s uphill speed.
Enter the rates into the chart. The distance is the same in both directions,
20
miles.
Since
D=rt
, we solve for
t
and get
t=
D
r
.
We divide the distance by the rate in each row and place the expression in the time column.
Rate
×
Time
=
Distance
Downhill
r
20
r
20
Uphill
r−5
20
r−5
20
Write a word sentence about the time.
The total time traveled was
6
hours.
Translate the sentence to get the equation.
20
r
+
20
r−5
=6
Solve.
20(r−5)+20(r)
40r−100
0
0
0
=
=
=
=
=
6(r)(r−5)
6
r
2
−30r
6
r
2
−70r+100
2(3
r
2
−35r+50)
2(3r−5)(r−10)
Use the Zero Product Property.
(r−10)=0
r=10
(3r−5)=0
r=
5
3
The solution
5
3
is unreasonable because
5
3
−5=−
10
3
and his uphill speed cannot be negative. So, Dennis's downhill speed is
10
mph and his uphill speed is
10−5=5
mph.
Check. Is
10
mph a reasonable speed for biking downhill? Yes.
Downhill:
10 mph
5 mph⋅
20 miles
5 mph
=20 miles
Uphill:
10−5=5 mph
(10−5) mph⋅
20 miles
10−5 mph
=20 miles
The total time traveled was
6
hours.
Dennis’ downhill speed was
10
mph and his uphill speed was
5
mph.
Answer:
x= -1, y = 6, z = 3
Step-by-step explanation:
let me solve it with Gaussian Elimination
Answer:
Step-by-step explanation:
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<span><span><span><span><span>(<span>5+4</span>)</span><span>(2)</span></span>+6</span>−<span><span>(2)</span><span>(2)</span></span></span>−1</span><span>=<span><span><span><span><span>(9)</span><span>(2)</span></span>+6</span>−<span><span>(2)</span><span>(2)</span></span></span>−1</span></span><span>=<span><span><span>18+6</span>−<span><span>(2)</span><span>(2)</span></span></span>−1</span></span><span>=<span><span>24−<span><span>(2)</span><span>(2)</span></span></span>−1</span></span><span>=<span><span>24−4</span>−1</span></span><span>=<span>20−1</span></span><span>=<span>19</span></span>
